Police in Siem Reap are on the lookout for what they suspect is a large group of ATM fraudsters following the arrest of another foreigner accused of attaching “skimming” equipment to ATMs in order to steal customers’ credit card information, police said yesterday.

Authorities allegedly spotted Bulgarian national Tsvetozar Nikolaev Stoyanov, 28, tampering with a cash machine in front of Siem Reap’s provincial hospital, according to Pheng Chenda Rath, chief of Siem Reap minor crimes police, who said Stoyanov claimed to have been working with an unnamed German.

The police had been tipped off by ABA Bank, which has a team in place to remotely monitor CCTV feeds from its ATMs.

Deputy chief of Siem Reap minor crimes police Hok Bunhav said he and his colleagues “suspect that [Stoyanov] is part of a bigger group that breaks into smaller groups”.

Three Bulgarians pled guilty to card skimming in Phnom Penh last November, and another, allegedly acting with a Romanian accomplice, was arrested in Siem Reap last month.

A 2015 US State Department report called Bulgaria “the number one source country for ATM and credit card skimming-related crimes in the world”, and said that Bulgarian gangs skim more than €50 million (about $56.2 million) around the world each year.

Europol found many Bulgarian criminal organisations are moving away from traditional crimes such as drug trafficking and theft in favour of skimming, which carries less risk and lighter sentences.